Drawing and bulking of synthetic polymer



out. 28, 1969 D G, JENKINS ETAL 3,474,62

` DRAWING AND BULKING oF SYNTHETIC POLYMER United States Patent O Us. c1. 57-34 11 claims ABSTRACT OF THE DISCLOSURE Two like undrawn yarns of e.g. polyamide are drawn together and overfed at not more than overfeed to a false twist crimping zone in which opposite twist-crimp is imparted, e.g. by friction means, to the two yarns severally, which are then optionally wound up together by plying to form a balanced-torque yarn.

This application is a continuation-in-part of our application Ser. No. 411,996, filed Nov. 18, 1964, now Patent No. 3,341,913.

The invention concerns improvements in or relating to the drawing and bulking of synthetic polymer yarns.

In order to product bulked yarns from undrawn synthetic polymer filaments as spun by their producer, it is necessary to draw the filaments and to bulk them.

Various ways of combining drawing and crimping are already known, such as by normally drawing a falsetwisted undrawn yarn and by false-twisting an undrawn yarn at a tension sufficient to draw it.

in most of the above processes, the emphasis has been on the assimilation of the bulking proces to the standard drawing process, with a view to obtaining the economic advantage of doing away with the bulking step as a separate step in the process of making bulked yarns.

Certain other side advantages may also accrue, particularly in regard to setting the crimp imparted in the bulking step. In some eases, the heat of drawing will be sufficiently high to enable any specific heat-setting apparatus to be dispensed with.

Economically and technically, however, not all arguments are in favour of bulking at drawing. Rather is productivity, from a given factory floor space, sometimes greater when drawing is performed at bulking; and the limitations of space imposed by adaptation of bulking devices to drawtwisting machinery can be avoided if the adaptation is the other way round.

Thus, in practice a better bulked yarn may be made more economically by first drawing undrawn yarn at bulking than can be made by bulking a yarn whilst drawing it.

Our invention is concerned specifically with both drawing undrawn yarn, and then bulking it by false twist crimping.

According to the invention, in a process for drawing and bulking drawable synthetic polymer yarns, two like undrawn yarns of a drawable synthetic polymer material are forwarded together, by feed means at a predetermined rate to a drawing zone, the yarns are drawn in said zone by drawing means operating at `a drawing rate at least twice that of said predetermined rate, the drawn yarns are forwarded from said drawing means substantially at said drawing rate and at a low degree of mechanical overfeed, preferably not greater than 20%, to a false twist crimping zone containing heat-setting means and two oppositely rotated false twisting means,

3,474,612 Patented Oct. 28, 1969 and the drawn yarns are severally crimped thereby yand together withdrawn from the false twist crimping zone by withdrawing means, and then collected in orderly manner.

Preferably the feed means and the drawing means cornprise roll assemblies; and preferably the drawing is located at a snubbing-pin positioned in the drawing zone, where heat may optionally be applied to the yarn to assist drawing. Optionally, also, the feed means may comprise nip rolls positioned to act on the yarn upstream of an accompanying feed-roll assembly, the purpose of the nip rolls being to avoid tension non-uniformities in the yarn at the feed roll assembly. In fact, a minor (e.g. 0.1% to' 10%) degree of drawing may take place between the nip rolls and the feed roll assembly.

By mechanical overfeed we mean that the speed ratio of the drawing means feeding the yarns into the false twist crimping zone and the withdrawing means withdrawing the yarns therefrom is such as to bring about an overfeed of the amount specified, although the freshly-drawn yarn itself will on account of its nature, contract lengthwise by some at least of this amount.

By arranging that the drawing shall have been completed just prior to arrival of the yarn at the false twist crimping Zone the benefits accruing from such propinquity can be obtained with a great measure of control.

The tension in the running yarn in the false twist crimping zone is the result of the establishment of equilibrium conditions between the linear contraction that takes place in the yarn immediately on release from the drawing tension and the linear relaxation afforded to it by the circumstance of the mechanical overfeed. Such tension, and the freshly-drawn st-ate of the yarn, are responsible for the enhanced crimping propensity of the yarn, according to the invention.

The drawing means, e.g. a draw roll, combines the function of drawing with the one of positive over-feed into the false twist crimping (and setting) zone, say, by some 7%-15% overall. One effect of false twist crimping freshly-drawn, over-fed yarn is to enable crimped yarn of the required properties to be obtained at a greater throughput than when ordinary drawn yarn is used as the supply (at a considerably lower degree of overfeed).

For instance, crimped multilament yarns of polyhexamethylene adipamide, having a drawn denier of 70 can be produced 50% faster if drawing at a draw ratio of 3.18 takes place immediately prior to false twist crimping by conventional false-twist spindles with an allied heater and the drawn yarn is over-fed to the false twisting zone by the draw roll at an overfeed of 131/2, cornpared rwith an overfeed of 2.7% normally employed when crimping drawn yarns. The essential characteristics of the crimped yarns, for instance their crimp rigidity, are unmpaired by the higher speed, whereas those of yarns ordinarily drawn for use as a drawn supply yarns on packages are reduced below an acceptable value when crimped at the above-mentioned overfeed of 2.7% at such higher speed.

An optional feature 0f the invention is the inclusion of air-jet means to act on the low tension span of yarn between the supply cakes and the feed rolls of the drawing means to effect some intermingling of the filaments of a singles yarn, or of all the filaments of a plurality of such yarns and hence to compact such yarns into a uniform entity, prior to bulking.

Alternatively, or in addition, such an air-jet means can be positioned downstream of the false twisting means for the same function.

The invention will now be described with reference to the accompanying drawing which is a line diagram of the yarn path containing the drawing and false twist crimping instrumentalities in respect of a preferred embodiment of the invention.

In the drawing, undrawn yarns Y1 and Y2 are withdrawn from supply packages (not shown) by feed roll assembly 79, comprising nip rolls 81 and separator roll S3 from which they pass into the drawing stage. Drawing takes place between the feed roll assembly and a draw roll assembly 85, comprising nip rolls 87 and separator roll 89, the point of draw being located by non-rotatable snubbing pin 91 around which the yarns are wrapped with one complete turn.

From the drawing stage, the drawn yarns now pass to the bulking stage consisting of false twisting and heat setting means. The yarn paths are separated from one another by thread guides 93, 95; and the separated yarns are then passed through electrical contact heater 97. From the heater, the yarns proceed to two contra-rotating friction false-twisting tubes 98, 99 which impart false twist to the yarns in opposite directions, the twists running back in the yarns, through the heat-setting zone, to the nip of the draw roll assembly. Ihe twists are then set on the upstream side of the twist-tubes; and the yarns are de-twisted immediately on leaving the tubes. The false-twisted, latently-bulked yarns are then led separately over grooves in a freely-rotatable guide roller 101, and are withdrawn from the bulking zone by the withdrawing means comprising a take-off roll assembly 103, consisting of driven roll 105 and its separator roll 107. The yarns are then forwarded to a wind-up assembly (not shown), for orderly collection.

In the operation of the preferred embodiment of the invention illustrated in the drawing, the undrawn yarns are withdrawn from their packages by the feed roll assembly, and then drawn between that assembly and the draw roll assembly by being stretched some 200%- 400%. From the draw roll assembly, the drawn yarns are over-fed to the false twist crimping stage, the overfeed being arranged by the lower peripheral speed of the take-oit roll assembly compared with that of the draw roll assembly, itself functioning additionally as the positive feed for the false twist crimping mechanism. The extent of overfeed between the draw-roll assembly and the false twist tubes themselves will generally be different from that between the two sets of rolls, owing to the tension imparted by the false twist tubes, whether such be of the friction variety shown or of the conventional type. The false twist imparted, say 80 turns per inch, runs back to the nip of the draw roll assembly and is set into the yarns by the contact heater, which is heated to, say, 230 C. for nylon 66 yarns. Nip rolls are required for the draw roll assembly to snub the false twist and prevent it running back to the separator roll, where its presence otherwise would cause the yarns to collide. From the take-Gif roll assembly, the two oppositelytwisted, `bulked yarns are positively forwarded to a windup, where the yarns are either plied or wound-up separatelyl A degree of overfeed, to allow some contraction of the yarns before wind-up, is normally afforded.

In an example of the invention, two supply yarns of 34 filaments each, undrawn polyhexamethylene adipamide were withdrawn over-end from their spinning cylinder packages mounted on a creel, withdrawal being elfected by the feed rolls of a yarn-drawing stage. The yarns were maintained separate throughout the drawing stage, being wrapped once around a stationary, unheated snubbing-pin and drawn at a draw ratio of 2.71 (giving drawn deniers of 70). From the draw rolls the two yarns were separately over-fed by 7.8%, and at a tension of 4 grams, to the false twist crimping stage. The overfeed was measured and maintained between the draw rolls (acting as feed rolls for the false twist bulking-stage) and the take-olf rolls. In the false twist crimping stage each yarn separately was led through a friction false twist tube, 80 turns per inch S twist being inserted in one yarn, and 80 turns per inch Z twist being inserted in the other,

between the tubes and the draw roll. The thus-twisted yarns were led in contact with a heated metal plate positioned upstream of the tubes at a temperature of 230 C. The yarn speed at the take-off rolls was 4U() feet/minute. Finally, the yarns were wound-up together on a ringspindle wind-up i.e. one including the normal balloon guide, to form a balanced-torque bulked yarn. The yarns had a crimp rigidity of 41, and an equivalent steam setting temperature (E.S.S.T.) of 111.

Although polyhexamethylene adipamide is the only synthetic polymer material instanced above, it is to be understood that the invention is applicable to all such materials in yarn form which are drawable and retract somewhat immediately after release from the drawing tension,

What we claim is:

1. A process for drawing and bulking drawable synthetic polymer yarns comprising forwarding together two separate, similar undrawn yarns of a ldrawable synthetic polymer material by feed means at a predetermined rate to a drawing zone, drawing said undrawn yarns in said zone by drawing means operating at a drawing rate at least twice that of said predetermined rate, forwarding said separate drawn yarns from said drawing means substantially at said drawing rate and at a low degree of mechanical overfeed not greater than 20% to a false twist crimping zone containing heat-setting means, separately and simultaneously oppositely false twisting and heat setting the drawn yarns, withdrawing and combining the heat set twisted yarn and collecting the yarn as a balance-torque yarn.

2. A process according to claim 1 in which the degree of mechanical overfeed through the false twist crimping zone is between 7% and 15%.

3. A process according to claim 1 in which the feeding and the drawing is accomplished by roll assemblies with the drawing roll assemblies acting as a positive feed for a positive feed type of false twist crimping mechamsm.

4. A process according to claim 3 in which the false twist is imparted by frictional means.

5. A process according to claim 4 in which the yarns are positively forwarded after withdrawing at a degree of overfeed to allow for contraction thereof before orderly collection by winding-up.

6. A process according to claim 1 in which the yarns are wound up together by plying.

7. A method for producing accurately balanced-torque stretch yarns or drawable synthetic polymer material in one continuous operation according to claim 6, comprising performing the following steps sequentially:

(l) feeding a pair of continuous filament yarns of identical characteristics and properties to a drawing zone,

(2) drawing said pair of filament yarns by application of the same drawing forces thereto,

(3) simultaneously, uniformly and synchronously false twisting each yarn of said pair in opposite directions and with sufficient false twist to run the twist in the yarns into the portions extending back to said drawing zone,

(4) subjecting said pair of yarns to a common heat setting zone to set said yarns with false twist,

(5) combining said oppositely twisted, heat set yarns to form a single yarn having a balanced torque,

(6) forwarding said combined, balanced-torque yarn to a collection zone at a speed less than the speed with which the yarns were forwarded to the false twisting zone, and

(7) collecting said balanced-torque yarn.

8. A method for producing accurately balanced-torque stretch yarns as in claim 7 wherein said yarns are synchronously false-twisted by subjecting each of said yarns to a plurality of uniform and equal rotational forces along the linear length thereof and at substantially opposite sides thereof by frictional inpingement upon the peripheral surface thereof to rotate the yarns each in an opposite direction.

9. Apparatus for drawing and bulking drawable synthetic polymer yarns in one continuous operation comprising in combination a source of a plurality of yarns, feed roll means driven at one peripheral rate of speed, draw roll means uniformly driven for each of said yarns near said feed roll means and driven at a peripheral rate of speed greater than the peripheral speed of said feed roll means, heater means near said draw roll means for heating said plurality of stretched yarns extended to pass thereover, synchronously oppositely driven false twist means adapted to twist one of said plurality of heated yarns brought into engagement therewith in one direction and another of said heated yarns in the opposite direction, said twisting being simultaneous, guide means for combining said plurality of false twisted yarns to form a balanced-torque yarn, overfeed roll means driven at a peripheral rate of speed less than the peripheral rate of speed of said draw roll means for forwarding said balanced-torque yarn brought into engagement therewith,

and means for taking up said balanced-torque yarn from said overfeed roll means.

10. Apparatus as claimed in claim 9, in Which said draw roll means comprises nip rolls.

11. Apparatus as claimed in claim 9 wherein said collection means includes means for applying a low plying twist to said combined yarn while being collected.

References Cited UNITED STATES PATENTS 2,890,568 6/ 1959 Willens 57-34 XR 3,063,124 11/1962 Hilleary et al 57-34 XR 3,069,837 I12/1962 Olson 57-34 XR 3,165,881 l/1965 DeMoncuit et al, 57-34 FOREIGN PATENTS 842,463 7/ 1960 Great Britain. 850,079 9/ 1960 Great Britain.

20 STANLEY N. GILREATH, Primary Examiner W. H. SCHROEDER, Assistant Examiner 

